The ability of a filtration system to remove particles is generally measured in terms of the logarithmic reduction value (LRV). For any given particles, the logarithmic reduction value is defined as: ##EQU1##
where:
C.sub.inf =Concentration of particle in the influent PA1 C.sub.eff =Concentration of particle in the effluent. PA1 i) measuring the filtrate flow rate through the membrane; PA1 ii) measuring the membrane bypass flow rate using integrity test measurements; and PA1 iii) estimating the logarithmic reduction value using the ratio of measured filtrate flow rate and measured bypass flow rate as follows: ##EQU2## PA1 (i) wetting the membrane; PA1 (ii) applying a gas pressure to one side of the membrane below the bubble point of the membrane pores; and PA1 (iii) measuring gas flow across the membrane, said gas flow including diffusive flow through the membrane and flow through leaks and defects in the membrane, said gas flow being related to any defects in the membrane.
The particle used in the calculation can be any particle of interest, for example, in the case of disinfecting systems it would typically be bacteria or viruses, but may also be suspended solids.